1. Field of the Invention
The invention generally relates to a control apparatus and in particular relates to a brightness control apparatus and a brightness control method.
2. Description of Related Art
Computers may be categorized into two types, i.e. military computers and general computers. The difference between the military computer and the general computer is that the military computer usually needs to be operable in harsh environments, e.g. high temperature or low temperature. Thus, the requirements for military computer in terms of operability at various ambient temperatures are much stricter than general computer. Factors, such as slimness and light weight which are important to the general computer, but are not the main concern for military computer.
When the military computer operates in harsh environments such as high temperature or low temperature, the control of the brightness of a display thereof is necessary for the normal operation of the military computer. For example, at high temperature, the brightness of the display needs to be decreased so as to prevent the display from showing black screen. At low temperature, the brightness of the display needs to be decreased to avoid excessive power consumption (because starting-up takes longer time at low temperature and the work of other components needs adjustment for heating). In addition, in a heavy load state, the brightness of the display also needs to be reduced to lower the power consumption of the overall system.
Before Windows operating system Windows 8 is introduced, the brightness of the display is controlled by a pulse width modulating signal outputted by an embedded controller. Therefore, free adjustment of the brightness is possible. In the structure of Windows 8, however, the brightness of the display is controlled by Windows Display Driver Model (WDDM). In other words, the brightness of the display is controlled by the pulse width modulating signal outputted by a platform controller hub (PCH) under control of a driver of the Windows Display Driver Model. Thus, the traditional method for adjusting the brightness of the display to achieve normal operation of the computer at high temperature, low temperature, or heavy load is not applicable.